1. Field of the Invention
The present invention relates generally to a method of controlling the traveling stability of a vehicle, and more particularly to a method of controlling the traveling stability of a vehicle, which can obtain the traveling stability of a vehicle by controlling braking force and driving force in understeering or oversteering of the vehicle.
2. Description of the Prior Art
Generally, an antilock brake system (ABS) is used to prevent locking of wheels by suitably controlling braking pressure applied to the wheels according to a slip rate calculated on the basis of wheel speed. A traction control system (TCS) is used to control the driving force of an engine so as to prevent excessive slip when vehicles suddenly start or accelerate.
The ABS and TCS can show excellent performance when a vehicle travels on a straight road. However, when the vehicle travels while turning along a curved road, understeering (plowing) may occur in which the vehicle excessively slants outwardly, as well as oversteering (spinning-out) in which the vehicle excessively slants inwardly.
Therefore, a vehicle stability system is required to stably control the position of the vehicle under any conditions that the vehicle travels in, that is, preventing the loss of steering of the vehicle. For example, when understeering occurs, in which the vehicle is pushed outwardly from a driver's desired traveling track while turning, braking force is applied to an inner rear wheel, thus preventing the vehicle from being pushed outwardly. When oversteering occurs, in which the yaw rate of the vehicle excessively increases while turning and the vehicle then slants inwardly from a driver's desired traveling track, an operation of applying braking force to an outer front wheel is required.
In order to control the vehicle stability while turning, the performance of the vehicle stability system is determined according to whether the system can exactly predict a driver's desired yaw rate for the vehicle, and apply suitable braking pressure to front wheels and rear wheels to enable the vehicle to travel on according to the predicted yaw rate.
Further, the control of vehicle stability must not deteriorate the performance of both the antilock brake system and the traction control system. Similarly, the antilock brake system and the traction control system must not have undesirable effects on vehicle stability.
Accordingly, in order to control vehicle stability suitably for the traveling state of the vehicle, it is preferable to cooperatively control vehicle stability in connection with the conventional antilock brake system and the traction control system while exactly predicting a driver's desired yaw rate for the vehicle.